People are increasingly relying on computing devices, such as tablets and smart phones, which utilize touch sensitive displays. These displays enable users to enter text, select displayed items, or otherwise interact with the devices by touching and performing various movements with respect to the display screen, as opposed to other conventional input methods, such as using a mouse or directional keys on a keyboard. Many mobile computing devices include touch sensitive displays that can detect multiple touches, such as where a user uses two or more fingers to provide concurrent input. These multi-touch enabled devices are programmed to interpret the movement of multiple touches over a period of time as user inputs to perform certain functions, such as panning or zooming the image on the display.
The touch sensitive displays can utilize a variety of technologies for detecting user touches. In projected capacitance touch sensitive displays, an array of conductive sensors are distributed across the face of the computing device, typically covering the image displaying portion of the device. Two types of projected capacitance systems have been used: mutual capacitance and self capacitance.
Mutual capacitance touch sensitive displays typically utilize rows and columns of conductive lines which are used to detect changes in the capacitive coupling between pairs of conductive lines caused by the presence of a user's finger. Self capacitance touch sensitive displays detect the capacitive load caused by the presence of a user's finger near a single conductive sensor. Each type of capacitive touch technology can provide certain advantages that the other type does not. Accordingly, there is a need for improved methods and systems for implementing both mutual and self capacitive touch sensing technology within a single display.